Personally if it's boiling hot like today I'm walking the streets shirtless. Too hot for a top and also I don't want tan lines that look like I've dipped my arms in gravy.
However it seems scourned on by some? Get a lot of disapproval as though it's the polite etiquette.
Strangely too - get lots of angry looks and comments from van driver blokes as though having your top off somehow signals you're ready for war?
Really don't get how upset being shirtless can make another grown man. Odd behaviour.